1. Field of the Invention
The present invention generally relates to the art of making a concrete wall which is insulated both on the inside and on the outside by using a formwork, made of foam plastic material such as expanded polystyrene, as a mold into which the concrete mix is poured, which mold is permanently secured to the concrete after the latter has set.
2. Description of the Prior Art
In present day practice, a formwork made of wood or metal panels held together in spaced parallel position by tie-wires and other appropriate connection means at their ends, is used to build a concrete wall. The formwork is expensive and its mounting and dismounting are time consuming and thus also costly. Furthermore, the resulting concrete wall is not insulated.
A formwork has already been proposed which is constituted by hollow modules fully made of insulating foam plastic material; the modules being disposed and stacked in the manner of a brick wall and concrete mix being thereafter poured into the assembled hollow modules acting as a mold which remain permanently secured to the concrete wall after the concrete has set. In this manner, not only is time being saved in setting up the formwork on site-appropriate tie-wires and tongue-and-groove joints being provided at the factory--but there is no time wasted in dismantling the formwork as in the old practice. Also, the very advantageous result is the production of a concrete wall which is fully and permanently insulated both on the inside and on the outside.
However, these known insulated formworks suffer severe drawbacks.
Indeed, because these modules are quite light, they tend to separate from one another by the pressure built by the concrete mix when being poured. Because of this, elaborate means must be provided, at the site and outside the formwork, to prevent such separation caused by lifting of the modules as the latter tend to float on the concrete mix, because of their lightness.
Also, the known formworks are built, as said above, from brick-like hollow modules molded in factory and formed of a pair of foam plastic panel-like sections held in space relationship by tie-wires or rods of which the ends are solidly embedded in the foam plastic, at the factory. The result is that a module is useful for making a concrete wall having only one predetermined thickness. It is therefore necessary for the manufacturer to keep a large inventory of modules of varying thicknesses to satisfy customers' demand.